Matilda needs at least 112$ to buy a new dress . she has already saved $40 . she earns $9 an hour babysitting .write and solve an inequality to find how many hours she will need o babysit to buy the dress .

112 is what it should be set less than or equal to because she needs at least this much money for the dress. So 112 should be equal to or less than the amount she earns total. 112≤? On the other side you need to put 40 because this is what she already has. You need to add 40 to 9x, x being the amount of hours she works. so your inequality is 112 ≤ 9x +40. 
From there subtract 40 on both sides and then divide by 9. Your answer should be 8 hours.

The discount is 8.70 . you dont tell us the percent of tax added so there is no way to find out, unless i'm not seeing anything. without tax its 37.70